This invention relates to screen printing and more particularly to a clamp and process for protecting printing screens and frames.
Screen printing has been used to print designs on mugs, cups, dishes, shirts, and other textiles and products for years. Screen printing can be accomplished with printing screens made of such silk, polyester, and fine mesh metal. The negative of the image to be printed is placed on the printing screen so that when ink flows through the screen only the desired image, pattern, illustration and/or words will be printed.
The printing screen is usually held in place by a rigid frame, such as a rectangular frame. It is important that the screen be held in place with the proper amount of tension against the frame to attain sharp accurate printing.
Printing screens and frames can be used for high volume printing and are regularly moved, assembled and disassembled. They are frequently bumped, knocked, thrown around, dropped, abused, mishandled and subject to rigorous tension, torsion, and compressive forces. As a result, printing screens often tear, puncture, fray or are scratched and printing frames are often damaged. Printing screens usually tear near the edges of the screens in closed proximity to the printing frame. Damaged printing frames can result in undesired loosening, twisting, or stretching of printing screens.
Damaged printing frames and torn printing screens often result in blurred printing, blotches, misalignment of colored images, undesired extraneous lines and ink markings, ruined prints, waste, and printed products of unacceptable quality. Substantial costs are incurred in print wastage, reprinting, replacing torn, frayed, or scratched printing screens, correcting loosened or twisted printing screens, and repairing or replacing damaged printing frames.
Over the years a variety of printing screens, frames and other equipment have been suggested. Typifying these printing screens, frames and other equipment are those shown in U.S. Pat. Nos.: 1,742,339; 1,874,476; 2,218,451; 2,299,628; 2,566,919; 2,693,205; 3,230,882; 3,273,497; 3,757,953; 3,859,918; 4,568,455; 4,863,156; 4,860,814; and 4,934,738. These printing screens, frames, and other equipment have met with varying degrees of success but have not been satisfactory to prevent tearing, fraying, and scratching of printing screens nor to prevent damage to printing frames.
It is, therefore, desirable to provide an improved apparatus and process which overcomes most, if not all, of the preceding problems.